The present invention relates to a thermosensitive image transfer recording medium capable of forming images having high image density and excellent image gradation, even on a receiving sheet having a rough surface, in particular, on a sheet of plain paper having poor smoothness, by application of heat to a thermofusible ink layer of the recording medium, for instance, through a thermal head or a laser beam application device so as to imagewise transfer a thermofusible ink composition contained in the thermofusible ink layer to the receiving sheet.
More particularly, the present invention relates to a thermosensitive image transfer recording medium comprising (i) a support material, (ii) a thermofusible ink layer formed thereon, comprising (a) a fine porous network structure made of a resin, and (b) a thermofusible ink composition held in the porous network structure, which comprises as the main components a thermofusible material which is solid at room temperature, a colorant and an oil component, and (iii) a thermofusible top layer comprising an oleophilic thermofusible material formed on the thermofusible ink layer.
Conventionally, there are known (i) a thermosensitive image transfer sheet comprising a support material and a sublimable dye layer formed on the support material, and (ii) a thermosensitive image transfer sheet comprising a support material and a thermofusible ink layer comprising a thermofusible material and a pigment which are homogeneously dispersed therein, capable of forming images on a receiving sheet by subjecting the thermosensitive image transfer medium to thermal printing.
The method using a sublimable dye, however, is superior in the reproduction of image gradation, but has the drawbacks that the thermal sensitivity is low and the durability of the reproduced image is poor. On the other hand, the method using a thermofusible material and a pigment is superior in thermal sensitivity and the durability of the produced images, but has the drawback that the image gradation is unsatisfactory.
Furthermore, there has been proposed a thermosensitive image transfer recording medium comprising a support material and a fine porous structure formed thereon, which contains a thermofusible ink composition consisting essentially of (a) a thermofusible material which is solid at room temperature and (b) a colorant. In comparison with the conventional thermofusible type recording media, the above proposed thermosensitive image transfer recording medium is improved on image gradation, but the images transferred to a receiving sheet having a rough surface, for instance, a sheet of plain paper having poor smoothness, are poor image quality and still unsatisfactory for use in practice.